The Soda Pop Dilemma

Okay. So, after a big argument with my husband this week I gave up my 1 Pepsi/Day habit. Once upon a time I drank 3-4, at a minimum, so 1 was so much better. Can someone please explain to me, how in my 20s, when I gave up pop, and dieted, and exercised I didn't lose a SINGLE pound. Not inches, not toning up, no ounces lost. Now I am approaching 40, and I have already lost 2+lbs. In just a few days....well, almost a week. Last Pepsi was Tuesday. It makes no sense to me what-so-ever. (Of course I am still starving for food, every second of every day, and I am afraid that I am destined to never make it back into my favorite pair of jeans...but I am trying.)